In math class, the girl to boy ratio is $3$ to $2$. If there are $12$ girls, how many boys are there?
A ratio of $3$ girls to $2$ boys means that there is a group of $3$ girls for every group of $2$ boys. If there are $12$ girls, then there are $4$ groups of $3$ girls each. Because we know the ratio is $3:2$ , there must be $4$ groups of $2$ boys each. There is a total of $8$ boys in math class.